Kumar, Abhineet (Cairn Oil & Gas, Vedanta Limited) | Prakash, Aditya (Cairn Oil & Gas, Vedanta Limited) | Singh, Alok (Cairn Oil & Gas, Vedanta Limited) | Bharati, Pradeep (Cairn Oil & Gas, Vedanta Limited) | Jayan, Binshu (Cairn Oil & Gas, Vedanta Limited) | Kothiyal, Manish (Cairn Oil & Gas, Vedanta Limited) | Patil, Bhushan (Cairn Oil & Gas, Vedanta Limited) | Sarma, Phanijyoti (Cairn Oil & Gas, Vedanta Limited)
An offshore drilling campaign comprising of four development wells was conducted to augment oil production from a field located off the western coast of India. All four wells were designed to be sidetracked from existing depleted wells of the field. Historically, preparing existing wells in the field for side-track took ~4 days/well of a drilling rig and associated spread cost. This paper presents a case- history of conducting side-track well preparatory activities by a rig-less well intervention spread leading to significant time and cost savings. This method was also the first instance of such an activity being conducted in an offshore environment in India.
Prior to actual side-track drilling from an existing well in a brown field, it is required to abandon the open zones in the existing well and prepare the well for casing window cutting for further drilling to a new sub-surface target. Typical preparation activities include multiple wireline runs to set/retrieve deep set and tubing hanger plugs, well killing, nipple-down X-mas tree, nipple-up BOP, wireline run to cut tubing, retrieval of existing completion and ultimately placement of cement plugs to abandon the parent wellbore. The routine approach in the organization for all previous offshore drilling campaigns was to utilize the offshore drilling rig for afore-mentioned well preparation activities. Substantial rig time was spent incurring the cost of entire rig spread for an average ~4 days/well equivalent to ~40% of total well completion time.
The paper elaborates on rig-less operations set-up consisting of Cementing and Wireline Units utilized to conduct well killing, placement of cement plugs, production tubing cutting and nippling down X-mas tree prior to the mobilization of the drilling rig at the platform. The only operation left for the drilling rig was to pull-out the existing completion string and then drilling operations could commence.
The execution of planned operations was flawless on three wells while one well posed technical limitation due to its high deviation. The rig less well preparation campaign was concluded incident free, ahead of schedule and within budget. This offline exercise prior to rig-move saved ~12 days of drilling campaign time which helped in cutting down on overall drilling campaign cost and also allowed the flexibility of adding more wells to the campaign within fair weather window.
While this was an effort to simplify operations and save costly drilling rig-time in a side-track drilling campaign by conducting some very critical operations offline, these methods can also be adopted for planning well abandonment and decommissioning activities in a mature field.
Grover, Kavish (Cairn Oil & Gas, Vedanta Limited) | Kolay, Jayabrata (Cairn Oil & Gas, Vedanta Limited) | Kumar, Ritesh (Cairn Oil & Gas, Vedanta Limited) | Ghosh, Priyam (Cairn Oil & Gas, Vedanta Limited) | Shekhar, Sunit (Cairn Oil & Gas, Vedanta Limited) | Agrawal, Nitesh (Cairn Oil & Gas, Vedanta Limited) | Das, Joyjit (Cairn Oil & Gas, Vedanta Limited)
For any typical water flood or polymer flood management, maintaining optimum Voidage Replacement Ratio (VRR) is most crucial for optimizing reservoir performance. In a typical patternflood, a single injector supports many nearby producers, determining its contribution to particular producer is subjective and has inherent uncertainties. To avoid these uncertainties in allocation factor, a novel approach using simulation model based voidage compensation on pattern by pattern basis has been proposed in this paper.
History matched simulation model, which has been sectored into 5-spot producer centric patterns, forms the basis of this study. Voidage replacements are analyzed on these producer centric 5-spot patterns. Sectoral voidage created is determined using change in hydrocarbon pore volume (HCPV), water pore volume (WPV) and production from the sector. Sectoral Voidage Compensation Ratio (or Pseudo VRR) thus calculated is representative of the net change due to injection and production. The advantage is that it does not require any numerical allocation factor, rather is based on fluid movements within a pattern as predicted by the simulation model. This method thus provides a new approach to analyze pattern performance.
Along with VRR, pattern wise recovery and interwell channeling/cycling are the key parameters for any water flood performance analysis. A workflow has been proposed to rank the patterns based on these parameters and categorizing them into problem buckets. Actions corresponding to each bucket have been proposed. This forms the basis of strategizing improvements in well-by-well and pattern-by-pattern performance for optimizing field performance.
Gurjar, Sahab Singh (Cairn Oil & Gas, Vedanta Limited)
In line Inspection (ILI) Interval are often based on conditions that are assumed constant over long sections of pipeline - perhaps entire pipeline systems. Many pipeline operators are following the fixed ILI Interval based on statuary requirement irrespective of different local corrosion growth conditions prevailing on the particular pipeline system. Scheduling the ILI based on maximum interval defined in statuary requirement may be very unrealistic and pose threats to the integrity of these pipelines. This technical paper discusses the importance of ILI Interval, corrosion growth rate analysis, recent development to determine the ILI Interval, an engineering approach to calculate appropriate ILI-RunInterval, mitigation plan to extend the ILI-RunInterval for particular pipeline system. This technical paper would enhance the awareness among the pipeline operators to appropriately calculate the ILI-Run Interval which would cost beneficial to pipeline operators in long term without any integrity threats.
Bhardwaj, Charu (Cairn Oil & Gas, Vedanta Limited) | Ranjan, Vishal (Cairn Oil & Gas, Vedanta Limited) | Jetley, Shailendra Kumar (Cairn Oil & Gas, Vedanta Limited) | Tiwari, Shobhit (Cairn Oil & Gas, Vedanta Limited) | Ghosh, Anirban (Cairn Oil & Gas, Vedanta Limited) | Sharma, Swapnil (Cairn Oil & Gas, Vedanta Limited) | Bohra, Avinash (Cairn Oil & Gas, Vedanta Limited) | Kumar, Abhishek (Cairn Oil & Gas, Vedanta Limited) | Beohar, Abhudai (Cairn Oil & Gas, Vedanta Limited) | Sharma, Sidharth (Cairn Oil & Gas, Vedanta Limited)
The Raageshwari Deep Gas (RDG) field, situated within Barmer Basin in the State of Rajasthan, India, was discovered in 2003. The field is a tight gas condensate reservoir, with excellent gas quality of approximately 80% methane, low CO2 and no H2S. Since the permeability (0.01 - 1 md) is low in this reservoir, hydraulic fracturing is required to get substantial recovery from the wells. The field has been under production since 2010. The development of this field has been carried out in three phases and more than 150 fracturing treatments have been pumped in this reservoir till date to achieve sustained economical production. This paper deals with the lessons learnt and changes implemented in choke design through various development phases of the field.
In the initial phase of field development, chokes with a low Flow Coefficient (Cv) were installed to meet the requirement of controlling the wells at low flow rates and high differential pressure. Later as the surface handling capacity increased, the chokes had to be de-bottlenecked, requiring additional Capex for new chokes. To avoid a similar scenario in the future, a comprehensive approach has been followed to envisage Cv requirement, considering well wise production profiles and surface handling capacities throughout the life of field. Since a single trim can't operate over the complete life-cycle of a well, trim interchangeability has been included in the choke design such that low and high Cv trims are interchangeable.
Pre-mature failures of trims were observed in initial phase and a root cause analysis was done to ascertain the reason. Based on the analysis, trim metallurgy has been changed from Tungsten Carbide to ASTM A276 Specific Stainless Steel Grade 440C. Trims with newly selected mettalurgy have been installed in the existing chokes.
The introduction of trim interchangeability has saved MMUSD 0.3 in the future Opex as the requirement of procuring altogether new chokes for late life period of wells is avoided. Initially failures in the trim bodies were observed as early as two months of commissioning but with the change in metallurgy zero failures have been observed with operational life of chokes being higher than four years. This has avoided significant downtime on wells and expenditure on regular trim changeovers.
Although Tungsten Carbide is one of the most common materials used for constructing trims world over, there could be specific cases where-in other metallurgy may add better value. The workflow followed in this paper will help select a suitable metallurgy and can impart a significant value to the industry.
The rapid progress of technology such as big data and analytics, sensors, and control systems offers oil and gas companies the chance to automate high-cost, dangerous, or error-prone tasks. Most oil and gas operators are starting to capture these opportunities and doing well to accelerate their efforts. Companies that successfully employ automation can significantly improve their bottom line operations.
While automation offers many potential benefits in the upstream value chain of exploration, development, and production and transportation, some of the biggest opportunities are in crude transport operations, such as increased safety, security and decreased down time. Given the increase in oil and gas industry's substantial transport operations, optimizing these operations are essential. Automation creates several opportunities to that end: maximizing accuracy and efficiency in transport operations
This article is based on the application of digital technologies in the field of Crude Oil Transportation for improving Safety and Security while reducing the overall time taken for Crude Transportation Operations at Suvali Onshore Terminal. Digitization and automation of crude transportation operations in oil & gas industry leads to elimination of crude pilferage, elimination of manual errors, efficient crude loading operations, real time monitoring of crude transport operations, ease of measurements, reduction in disruption of crude tanker operations etc
Agrawal, Nitesh (Cairn Oil & Gas, Vedanta Limited) | Chapman, Tom (Cairn Oil & Gas, Vedanta Limited) | Baid, Rahul (Cairn Oil & Gas, Vedanta Limited) | Singh, Ritesh Kumar (Cairn Oil & Gas, Vedanta Limited) | Shrivastava, Sahil (Cairn Oil & Gas, Vedanta Limited) | Kushwaha, Malay Kumar (Cairn Oil & Gas, Vedanta Limited) | Kolay, Jayabrata (Cairn Oil & Gas, Vedanta Limited) | Ghosh, Priyam (Cairn Oil & Gas, Vedanta Limited) | Das, Joyjit (Cairn Oil & Gas, Vedanta Limited) | Khare, Sameer (Cairn Oil & Gas, Vedanta Limited) | Kumar, Piyush (Cairn Oil & Gas, Vedanta Limited) | Aggarwal, Shubham (Cairn Oil & Gas, Vedanta Limited)
The objective of this paper is to present a suite of diagnostic methods and tools which have been developed to analyse and understand production performance degredation in wells lifted by ESPs in the Mangala field in Rajasthan, India. The Mangala field is one of the world’s largest full field polymer floods, currently injecting some 450kbbl/day of polymerized water, and a significant proportion of production is lifted with ESPs. With polymer breaking through to the producers, productivity and ESP performance in many wells have changed dramatically. We have observed rapidly reducing well productivity indexes (PI), changes to the pumps head/rate curve, increased inlet gas volume fraction (GVF) and reduction in the cooling efficiency of ESP motors from wellbore fluids. The main drivers for the work were to understand whether reduced well rates were a result of reduced PI or a degredation in the ESP pump curve, and whether these are purely down to polymer or combined with other factors, for example reduced reservoir pressure, increasing inlet gas, scale buildup, mechanical wear or pump recirculation.
The methodology adopted for diagnosis was broken in 5 parts – 1) Real time ESP parameter alarm system, 2) Time lapse analysis of production tubing pressure drop, 3) Time lapse analysis of pump head de-rating factor, 4) Time lapse analysis of pump and VFD horse power 5) Dead head and multi choke test data. With this workflow we were able to break down our understanding of production loss into its constituent components, namely well productivitiy, pump head/rate loss or additional tubing pressure drop. It was also possible to further make a data driven asseesment as to the most likely mechanisms leading to ESP head loss (and therefore rate loss), to be further broken own into whether this was due to polymer plugging, mechanical wear, gas volume fraction (GVF) de-rating, partial broken shaft/locked diffusers or holes/recirculation. In some cases a specific mechanism was compounded with an associated impact. For example, in ESPs equipped with an inlet screen, heavy polymer deposition over the screen was resulting in large pressure drops across the screen leading to lower head, but this also resulted in higher GVFs into first few stages of the pump, even though the GVF outside the pump were low, leading to further head loss from gas de-rating of the head curve. With knowledge of the magnitude of production losses from each of the underlying mechanisms, targeted remediation could then be planned.
The well and pump modelling adopted in the workflow utilise standard industry calculations, but the combination of these into highly integrated visual displays combined with time lapse analysis of operating performance, provide a unique solution not seen in commercial software we have screened.
The paper also provides various real field examples of ESP performance deterioration, showing the impact of polymer deposition leading to increased pump hydraulic friction losses, pump mechanical failure and high motor winding temperature. Diagnoses based on the presented workflow have in many cases been verified by inspection reports on failed ESPs. Diagnosis on ESPs that have not failed cannot be definitive, though the results of remediation (eg pump flush) can help to firm up the probable cause.
Hydraulic fracturing stimulation is considered a successful development technique in tight gas reservoirs. However, these expensive operations sometime underperform due to ineffective fracture fluid (FF) clean-up. This paper concentrates on FF clean-up efficiency for a Multiple Fractured Horizontal Well (MFHW) completed in both homogeneous and naturally fractured (NF) tight gas reservoirs. The emphasis is on NF reservoirs that make up a large percentage of tight gas assets, as their clean-up efficiency has received little attention.
In this study, two numerical simulation models, i.e. a single-porosity single-permeability and a dual porosity-dual permeability model representing a homogeneous and a NF tight gas reservoir respectively, were used. Simulations were conducted on a MFHW with seven hydraulic fractures (HF). The process comprised of injection of FF, then a soaking time (ST) followed by production. The impact of various parameters which includes ST, FF viscosity, pressure drawdown and parameters pertinent to relative permeability and capillary pressure in matrix, hydraulic and natural fractures, were evaluated.
In addition, based on a newly proposed treatment process that generates in-situ pressure and thermal energy that breaks gel viscosity, the effect of resultant viscosity reduction and local pressure increase, for improving the clean-up efficiency was also assessed. In these simulations, and due to uncertainty in its value, NF permeability was varied over a wide range. For conclusive purposes, Gas Production Loss i.e. GPL (%) defined as the difference in total gas production between the completely clean and un-clean cases as a percentage of the clean case, after a specific production period was used. This paper prioritizes the impact of pertinent parameters and highlights the influence of thermochemicals on the clean-up efficiency thereby justifying its commercial practicality. For instance, it is shown that the presence of NFs results initially in higher GPL but then GPL reduces significantly. Reducing the FF viscosity improves clean-up significantly especially for the NF models as NFs are the main contributor to the gas and FF flow from the reservoir to surface via hydraulic fractures. The sometimes non- monotonic trend of GPL variations, depends on the specific combination of NFs’ permeability and FF viscosity which results in the certain fluid invasion profile and mobility in the system.
The paper emphasis is on the impact of thermochemicals and natural fractures on the cleanup up efficiency of hydraulic fracturing stimulations that should be optimized to reduce cost, thereby increasing the profit from these projects.
Vijayvargia, Utkarsh (Cairn Oil & Gas, Vedanta Limited) | Goyal, Rajat (Cairn Oil & Gas, Vedanta Limited) | Anand, Punj Sidharth Saurabh (Cairn Oil & Gas, Vedanta Limited) | Tiwari, Shobhit (Cairn Oil & Gas, Vedanta Limited)
Raageshwari Deep Gas field is located in RJ/ON 90/1 Block in western India is a retrograde gas condensate unconventional volcanic reservoir. It consists of streaks of low permeability sand which require hydraulic fracturing to achieve commercial production. Plug and perf stage technology along with limited entry was used to ensure that most of the productive pay was stimulated. Production data, Frac and Reservoir parameter were evaluated vis-à-vis Productivity Index (PI) and interdependencies were understood.
Multiple stages in a particular well were stimulated by hydraulic fracturing with each stage having from 1 to 6 perforation clusters to ensure maximum kH coverage. Different treatment designs varying in job size, proppant type, concentration and pumping rates were prepared and executed based on the formation type, net pay and petrophysical properties. After flowback and initial cleanup, the wells were hooked to the production facility. Memory production logging was then conducted in a time phased manner and the interpreted data was used to determine the PI evolution of individual cluster of all the 93 stages in 15 wells.
Time lapse PI of individual clusters as well as specific stages were plotted against: Proppant pumped per net pay Average permeability Effective porosity Total proppant pumped Elevation depths of the Fatehgarh, Basalt and Felsic formations of the reservoir stretching from north to south of the field.
Proppant pumped per net pay
Total proppant pumped
Elevation depths of the Fatehgarh, Basalt and Felsic formations of the reservoir stretching from north to south of the field.
Important observations resulted from this exercise such as: The top most basalt stages are attributing a large portion of the 15 wells total cumulative production. It outperformed the shallower Fatehgarh sands which were thought to be more prolific. Well PI clearly supports the changes expected in the reservoir quality from north to south of the field and is in line with the OH logs. PI of wells in a particular area shows gradual improvement in contrast to the other wells PI. Positive effects of flowing back an inferior quality pay before fracturing the upper superior quality pay.
The top most basalt stages are attributing a large portion of the 15 wells total cumulative production. It outperformed the shallower Fatehgarh sands which were thought to be more prolific.
Well PI clearly supports the changes expected in the reservoir quality from north to south of the field and is in line with the OH logs.
PI of wells in a particular area shows gradual improvement in contrast to the other wells PI.
Positive effects of flowing back an inferior quality pay before fracturing the upper superior quality pay.
This study will not only assist in determining the optimum proppant pumped per net pay height for different formations but also facilitate in eliminating frac stages in a well which would result in significant cost reduction in upcoming development campaign of 42 wells.
This holistic workflow will be used for refining the number of frac stages in a well as well as determining an ideal proppant quantity for a particular stage in volcanic pays. Detailed analysis of production data supported in identifying the key frac and reservoir parameters which subsequently will aid in improving hydraulic fracturing efficiency. Representative case histories of production results assisted in finalizing well services activities to improve the overall well PI.